Complex of the methyl esters of 3-amino-2,5-dichlorobenzoic acid and 2,5-dichloro-3-nitrobenzoic acid

ABSTRACT

A novel complex which is formed when essentially equimolar proportions of the methyl ester of 3-amino-2,5-dichlorobenzoic acid and the methyl ester of 2,5-dichloro-3-nitrobenzoic acid are heated together which complex shows herbicidal activity.

United States Patent [1 1 3,681,429 Graham et al. 1 Aug. 1, 1972 [54]COMPLEX OF THE METHYL ESTERS [56] References Cited F 3-A 2 Y gg UNITEDSTATES PATENTS NITROBENZOIC ACID 3,530,181 9/ 1970 Soloway et al...260/471 R Inventors: David E. Graham, Westfield; Thomas Schulze,Elizabeth; Marvin M. Fein, Westfield, all of NJ.

Assignee: GAF Corporation, New York, NY.

Filed: March 11, 1970 Appl. No.: 18,768

U.S. Cl. ..260/471 R, 71/111 Int. Cl ..C07c 101/54 Field of Search..260/471 R Primary ExaminerLorraine A. Weinberger Assistant Examiner-L.Arnold Thaxton Attorney-Samson B. Leavitt and Walter C. Kehm 5 7]ABSTRACT 1 Claim, No Drawings '1 COMPLEXOFTHEME'IHYLES'I'ERSOF 3-AMINO-2,5-DICHLOROBENZOIC ACID AND 2,5- DICHLORO-3-NITROBENZOIC ACID Theinstant application is directed to a novel complex of the methyl estersof 3-amino-2,5- dichlorobenzoic acid and 2,5-dichloro-3-nitrobenzoicacid.

The individual components of the novel complex of the instant inventionare well known herbicidal compounds which exhibit exceptionally highdegrees of selectivity for undesirable vegetation and noxious weedswithout adversely affecting the desirable crops. These compounds arediscussed in detail in US. Pat. Nos. 3,013,873 and 3,014,063, thedisclosures of which are incorporated herein by reference. It is noted,how ever, that these compounds have been found to be particularlyexpensive, and therefore, the use thereof has been somewhat limited. The3-arnino-2,5- dichlorobenzoic acid compound and its esters have beenpreferred over the 2,5- dichloro-3-nitrobenzoic acid esters inasmuch asthe amino derivative has a lower volatility and therefore a lowerphytotoxicity on a number of desirable crops (e.g., on soybeans ortomatoes, particularly when applied to such crops grown in sandy soilsin warmer areas such as the southern United States). While the aminoform is the preferred form, it is noted that said amino form is producedby reduction of the nitro derivative, the amino derivative isnecessarily substantially more expensive than the nitro derivative, andthe expense thereof has limited its use to some extent. The novelcomplex of the instant invention, however, has been found to havesubstantially the same low volatility as the amino derivative above andsimilar low phytotoxicity on soybeans, tomatoes and a number of otherdesirable crops; however, said complex requires only half as much of themore expensive amino derivative for its production inasmuch as it is acomplex of the 3-amino-2,5- dichlorobenzoic acid ester and the2,5-dichloro-3- nitrobenzoic acid ester, and is thus substantially lowerin cost than the amino derivative.

As a result of applicants efforts, they have unexpectedly found thatwhen one heats the methyl ester of 3- amino-2,5-dichlorobenzoic acid inthe presence of the methyl ester of 2,5-dichloro-3-nitrobenzoic acid,one obtains a complex thereof which complex is not a simple mixture ofthe two compounds. While the exact form of complexing is not known, ithas definitely been shown that the product obtained as a result of thecomplexing, is different from a mere physical mixture of the individualingredients as is evidenced by the lower volatility of the complex overthat of a mere mixture. From the infra-red curves of this novel complex,it appears that the amino group of the 3-amino-2,5- dichlorobenzoic acidester is involved in the complex formation. Further physical data willbe presented hereinafter. to substantiate the complex formation.

The novel complex of the instant invention is readily synthesized bymixing 3-amino-2,5-dichlorobenzoic acid methyl ester and the2,5-dichloro-3-nitrobenzoic acid methyl ester and heating the resultingmixture. Such heating is preferably carried out at a temperature of atleast about 80C. (the melting point of the 2,5-

dichloro-3-nitrobenzoic acid methyl ester). A preferred temperaturerange for heating is about from C. to about 100C. or slightly higher.The mixture of the two individual methyl esters may be heated in bulkor, if desired, the heating step may be affected in an inert solvent,preferably a solvent such as methanol in which each of the individualmethyl esters is soluble but in which the novel complex of the presentinvention is relatively insoluble. In place of heating the mixture ofthe esters, the novel complex of the present invention may be formed bysubjecting such mixture to X-ray diffraction conditions or by intimatelygrinding the two esters (in solid form) together. Since the novelcomplex of the present invention is composed of essentially equal molarproportions of the two methyl esters, it is preferred to mix the twoesters in substantially equimolar proportions. However, a substantialexcess of either of the methyl esters may be employed, with the excessremaining in the final product or if desired, the excess may be removedand recovered from the essentially equimolar complex which is formed byseveral means such as crystallization.

The resultant complex has been thoroughly tested resulting in theconclusion that in fact a chemical complex results rather than a mereadmixture of the individual ester components. That is to say, the3-amino- 2,5-dichlorobenzoic acid methyl ester has a melting point ofapproximately 64.566C. The 2,5-dichloro- 3-nitrobenzoic acid methylester has a melting point 80-8 l .5C. Whereas, an equimolar complex ofthe two esters has been found to have a melting point of 86 C., thusleading to the belief that a complex rather than an admixture wasformed. It is further noted that a mere blend or admixture of the twocomponents when heated from 25l00C. clearly exhibits three distinctmelting points, one at 63, one at 75 and one between 82 and 85 thuscorresponding directly to the in- .dividual components of the blend andthe novel complex of the instant invention which results from theheating process. Upon further testing, it was found that when themixture of the blend tested above was cooled to room temperature andre-heated, the melting points of the individual methyl esters completelydisappeared and only the melting point of the novel complex of theinstant invention was found to bepresent. Thiswas explained when it wasfound that there was a partial formation of novel complex of the instantinvention below 80C. during the first heating from 25l00C. and thereaction was completed while heating to C. the second time.

In addition to the differential thermal analysis discussed above,thermogravimetric analysis demonstrated similar behavior. X-raydiffraction studies were also run on each of the individual esters,i.e., the methyl ester of 3-amino2,5-dichlorobenzoic acid and the methylester of 2,5-dichloro-3-nitrobenzoic acid, the complex of the instantinvention and an equimolar blend of each of the methyl esters. Thesamples were subjected to X-ray analysis using CuKa radiation at 40 KVand 35 ma. lt was found that the methyl ester of 3-amino-2,5-dichlorobenzoic acid is characterized by intense reflection at11.1 A spacing, by reflection of medium intensities at 4.39 A and 3.53 Aand low intensity reflections at 3.97 A, 3.80 A, 3.70 A, 3.65A, 339A,3.27 A, 3.24 A, 2.96 A, 2.73 A, 2.52 A, and 2.48 A spacings. The methylester of 2,5dichloro-3- nitrobenzoic acid is characterized by highintensity reflections at 8.75 A, 4.39 A, 4.26 A, 3.61 A and 3.11 A, byreflections of medium intensity at 4.03 A and 3.27 A, and by lowintensity reflections at 4.15 A, 3.74 A, 3.15 A, 2.96 A, 2.90 A, 2.84 A,2.78 A, 2.59 A, and 2.58 A spacings. As clearly distinguished therefromthe novel complex of the instant invention is characterized by highintensity reflections at 1 1.47 A, 6.80 A, 4.34 A, and 3.46 A, 2.90 A byreflections of medium intensity at 4.75 A, 3.91 A, 3.65 A, 3.40 A, 3.03A, 2.54 A, and 2.33 A, and by low intensity reflections at 9.4 A, 8.75A, 5.53 A, 3.21 A, 3.15 A, 2.78 A, 2.73 A, 2.64 A, 2.41 A, and 2.32 Aspacings. Furthermore, the equimolar blend of each of the above esterswas found to have an X-ray diffraction pattern similar to the novelcomplex of the instant invention. However, as was noted above, it hasbeen found that under X-ray analysis conditions the novel complex of theinstant invention is formed thus explaining this result.

Table 1 below summarizes the spacings and relevant intensity of theX-ray reflections of each of the above tested samples. As will readilybe appreciated, this summary clearly demonstrates that a complex isformed of the individual methyl esters rather than a mere admixturethereof.

Amiben Dinoben Amiben/Dinoben Methyl Methyl Methyl Ester Ester EsterEquimolar Blend Spacing of Reflection D A IuIMsI: III;IIIIII8I I I I I0051 I 550m soul til I I 8| al I I 3031 fiI I I I :11 I I smIssssl IE! II I..I s

lllO OllllUIlll-llll\\0 As was discussed above, the novel complex oftheinstant invention has been found to be an extremely useful herbicidein light of its low volatility and furthermore relatively low cost inlight of the fact that only one-half of the more expensive aminocomponent is necessary for effectiveness. Furthermore, crop damage as aresult of the use of a high level of the individual herbicides isdecreased in light of the fact that only one-half thereof is necessaryfor effective action. The complex of the instant invention is anequimolar complex comprising approximately one-half of the methyl esterof 3-amino-2,5-dichlorobenzoic acid and one-half of the methyl ester of2,5-dichloro3-nitrobenzoic acid, each of which esters has the followingformulas, respec- The instant invention will now be explained in moredetail in connection with the following examples thereof. It is to benoted, however, that the instant invention is not deemed as beinglimited thereto.

EXAMPLE I Fifty-five gm (0.25 moles) of methyl-2-arnino-2,5-dichlorobenzoate and 62.5 gm (0.25 moles) of methyl2,5-dichloro-3-nitrobenzoate were mixed and methanol was added to atotal volume of 300 cc. The mixture was heated to solution and thencooled to room temperature with agitation. A crop began to crystalize at48C. The crop was filtered at room temperature and washed with threeportions of 25 cc ice cold methanol and air dried, resulting in 89.4 gm,m.p. 85-86C. Two more crops were obtained by concen tration, giving atotalof 113.8 gm of the compound, 96.8 percent of theory. Analyticaldata for the first crop of product (complex) crystals was as follows:

Theory for equi- Found molar compoundMethyl-2-5-dichloro-3-nitrobenzoate by TiCl 56.1 53.1Methyl-3-amino'2,5-dichlorobenzoate by diazotization 45.3 46.9 Totalchlorine, Parr Bomb 29.8 30.2 Labile chlorine, pipen'dine method 7.867.57

Vapor Phase Chromatography:

50. 30 percent methyl-2,5-dichloro- 3-nitrobenzoate 49.3 1 percentmethyl-3-amino-2,5-dichlorobenzoate Mixed melting points:

A. percent methyl-2,5-dichloro-3-nitrobenzoate (mp. 80. 5-8 1), 20percent compound 74-78.5.

B. 80 percent methyl-3-amino-2,5-dichlorobenzoate (mp. 64.566C 20percent compd. 61 .5-83C.

EXAMPLE 11 4.40 gms of methyl-3-amino-2,5-dichlorobenzoate 0.02 moles)and 5.00 gm. methyl-2,5-dichloro-3- nitrobenzoate (0.02 moles) werethoroughly mixed and heated gradually in a melting point apparatus withthe following results:

58.5 softening 65 continues to sofien 69 appears to fuse 69-72 goescompletely solid 75 spots 81 begins to melt melts (most melted 8485C)The melting point tube was cooled to solidify and the melting pointtaken. It was solid to 80C., softened at 80 and melted at 8485.5C.

EXAMPLE III Five gm methyl-2,5-dichloro-3-nitrobenzoate (.02 moles) andgm methyl-3-arnino-2,5- dichlorobenzoate (0.046 moles) were mixed andenough methanol added to form 130 cc. of mixture. The mixture was heatedto solution and cooled to approximately 5C. with agitation. The crop wasfiltered, washed with ice cold methanol, and air dried giving 7.1 gm ofthe compound, mp. 85 .586C. A second crop,

1.6 gm, m.p. 8485C, was obtained by concentrating the filtrate. Totalyield of the compound was 8.7 gm 92.5 percent of theory.

EXAMPLE IV The method of Example Ill was followed using an excess ofmethyl-2,5-dichloro-3-nitrobenzoate, a 72.8 percent yield of a somewhatless pure material was isolated, m.p. 82.5--84.5C.

, EXAMPLE v 0.1 l grams of methyl-3-amino-2,5-dichlorobenzoate and 0.125grams of methyl-2,5-dichloro-3- nitrobenzoate were charged to a smallvial along with several agate balls and the vial stoppered and place ona laboratory vibrator for 0.2 hours at ambient temperatures. The thusproduced product has a melting point of 8384.5C.

When subjected to infrared analysis, the curve for the product wasessentially the same as that for the product of Example 1 above showingthe same differences from the infrared curves for the two startingesters.

EXAMPLE VI The novel complex of the instant invention was tested todetermine its herbicidal activity. The compound was applied inpre-emergence tests at a rate of 8 pounds/acre. Visual observations wererecorded with the following results:

Test Plant: Visual Observations Wheat No observable injury. Corn Noobservable injury. Onion Sets No observable injury. Sna beans Noobservable injury. Soy ans No observable injury. Wild Oats Moderateinjury. Foxtail Total kill.

R e rass Severe inu Ci a grass Total kill? ry Johnson Grass Severeinjury. Dock Severe injury. Mustard Total kill. Pigweed Total kill.Lambs Quarter Total kill. Chickweed Total kill.

